SOUNDINGS, DEEP SEA. Under the word LEAD-LINE a general description has been given of the process of sounding in anchorages and moderate depths upon the coast. Deep-sea sounding requires totally different apparatus. Prior to about 1350, the question of deep sea sounding was purely geographical and physical. To know the extreme depths of the ocean was but the natural march of that pro gress which had measured arcs of the meridian, and obtained the altitudes of the highest mountains on the face of the globe; and to descend to the mysteries of the earth's submerged surface, was but the obvious consequence of that insatiable desire for investigation which seems to characterise the minds of men of this particular epoch. lint it is no longer a purely scientific question, since it has become a matter of urgent necessity to find, at the bottom of the ocean, a rest for the telegraph-wire.
With the exception of a few spirited researches, chiefly of a private character, little in the way of systematic soundings had been accom plished ; though we must not overlook the advantages which deep-sea sounding received from the investigations ordered by Congress in 1849. The conduct of further and more elaborate experiments was confided to Lieutenant Maury, U.S.N., who was empowered by the Congress of the United States of America to equip a small schooner of 100 tons called the Palley, for various scientific purposes ; among them it was specially required that her commander, Lieutenant J. C. Walsh, U.S.N., should attempt to reach the bottom of the sea once in every 200 miles in crossing. the Atlantic. Up to this time no particular apparatus for taking deep soundings had been in use: the ordinary round shot slung with strips of canvas was the usual means employed. It was found extremely difficult to determine in some cases the period at which the shot reached the bottom ; the weight of some thousands of fathoms of line, and the influences of current and drifting of the vessel, rendered the exact depth attained only appreciable by long experience. The Fancy was, moreover, found too small a vessel for the purpose; the result, however, of the cruise reflects great credit on the commander, since he established the fact, that in some places the depth of ocean was more than 5700 fathoms, or was above six English miles ! thus exceeding the height of the most lofty known mountain. This was the greatest
depth that had been measured, without finding the bottom, and was attained on the 15th November, 1849, latitude 31° 59' N., and longi tude 58° 43' W. The time used in the descent of the line to this enormous depth was only 1 hour, but the line at last broke at the reel, losing the whole 5700 fathoms. We are assured by Lieutenant Maury, that the descent of the sounding line was accomplished without any jerks or checks, beyond those of the friction bands to give uniformity to the descent, so that the weight could not have touched the bottom, and was a fair straight up and down experiment. In this memorable sound*, the lead had a Stellwagen cone fitted to it, and a small apparatus weighing 6 lbs., for ascertaining the depth reached. The liue was of steel wire of the best English manufacture. In May, 1850, the United States again determined on exploring the deep sea. Considerable attention was paid to every requisite, and the Albany, Captain Platt, was next equipped for this service; the prin cipal locality of her observations was to be the Caribbeau Sea. Instead of steel wire, this ship was fitted with about 40,000 fathoms of twine, weighing about 150 fathoms to the pound. This was usually attached to a 32 lb. shot, which was allowed in its descent to take the turn from the reel without control. After various failures, and the loss of I much lino and several shot, a useful list of soundings was obtained and which are described in Lieutenant Maury's work. The principal result of these experiments was the proving that in no part of the Gulf of Mexico is the depth greater than 1000 fathoms. It became evident, however, that with a fixed weight, it is extremely difficult to determine the exact depth when the bight of the line is swept off by an under-current, which, even when the shot rests upon the ground, continues to take the line from the reel with scarcely diminished velocity. This would have a general tendency to give exaggerated depths.